Arrangement in tube heat exchangers with tubes of the plate or flat type



H T I W E MP Y R T ma MFQ T MA 1 REEZ HT A A M B M .U E Hd .NTR G Tic... m B GU A nT R A Sept. 2, 1969 Fig. 4

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70m? GUSTAV FRED/WK MAR/ 43A 75/ INVENTOR. 8; w 67 ATTORNEY.

United States Patent 3,464,488 ARRANGEMENT IN TUBE HEAT EXCHANGERS WITH TUBES OF THE PLATE 0R FLAT TYPE Tore Gustav Fredrik Marmsater, Vallingby, Sweden, as-

signor to AB Rosenblads Patenter, Stockholm, Sweden, a corporation of Sweden Filed Aug. 21, 1967, Ser. No. 661,941 Claims priority, application Sweden, Aug. 22, 1966, 11,281/ 66 Int. Cl. F28f 3/14 US. Cl. 165-166 1 Claim ABSTRACT OF THE DISCLOSURE A heat exchanger particularly for high pressures, having a bundle of tubes comprising elongated plate-shaped or flat heat transferring tubes of mainly rectangular crosssection, which also may be referred to as hollow lamellae, arranged side by side with open spaces between the tubes at the longitudinal edges thereof. The heat exchangers are assembled by joining opposing pairs of halves of successive tubes together by welding spacer elements between them, and then welding the edges of each of the halves to the edges of adjacent paired halves to form an assembly of spaced tubes.

The main object of the invention is to make it possible to conduct contaminating fluids both externally of the tubes and through the tubes where tubes of the plate or flat type are utilized exposed to high pressure. According to the invention this possibility is attained by the combination of the following features: (1) in known manner the tubes consist of two substantially plane or flat side walls of thin sheet metal arranged in opposed relationship and welded together substantially only along their lateral edges and (2) in a known manner the side walls of adjacent tubes defining said open spaces are separated by means of distance or spacing members generally having the shape of spigots and bridging the space between said side walls. A plurality of such spigots are distributed within said space and the side Walls are welded together by means of said spacing members.

Background of invention Generally, bundles of tubes of the plate or fiat type as well as bundles of tubes with circular cross-section, are arranged within a casing enclosing the bundle. In this casing one heat exchanging fluid flows externally of the tubes while the other heat exchanging fluid flows through the tubes. It is also conventional to arrange the bundle of tubes withdrawable from the casing so as to make the interspaces between the tubes easily accessible for inspection and cleaning by mechanical means. From this point of view flat tubes are superior to circular tubes in simplicity of inspection and accessibility of all parts of the heat transferring walls in said interspaces. A further important advantage is that flat tubes facilitate the provision of a compact bundle of tubes with a large heating surface in which the flowing conditions (1) in the tubes and (2) in the major section of their interspaces are as equal or regular as possible.

However, the very restricted capacity of the flat tubes to resist interior and external overpressure without deformation of the side walls has caused great difficulties in utilizing them for high pressures. Hitherto, each tube separately has been provided with a plurality of spacing members distributed within the tube and arranged between the side walls so as to be rigidly connected to each such side wall whereby the side walls will be stayed or supported. In the first place this results in the disadvantage that if a contaminating fluid, for example ice containing scale forming or solid components is passed through the tube, precipitations from the fluid will be collected at and around said spacing members which also form obstacles to an effective internal cleaning of the tube with mechanical means. Such a heat exchanger may thus be utilized only when at least one of the heat exchanging fluids is sufliciently clean to be conducted through the tubes since the other fluid, if contaminating, has to be conducted within the casing outside the tubes in the spaces between the tubes. Such spaces may be cleaned, the bundle of tubes having been withdrawn, but this task is inconvenient. However, although such conducting of the contaminating fluid within the casing is possible on account of the possibility of cleaning and may be the only solution of the cleaning problems in this type of tube construction, it is nevertheless frequently inappropriate in view of known difliculties to design the paths of flow, especially adjacent the inlets and outlets in such a manner, that no pockets will be formed in which precipitations from the contaminating fluid may be concentrated around considerable portions of the tubes.

In bundles of tubes of circular cross-section having an easily cleanable cross-sectional area it is of course in such cases possible to conduct the contaminating fluid through the tubes instead of around them. In doing so it will also be possible if necessary at the same time to conduct such a fluid outside the tube, that is to say to utilize the heat exchanger for two contaminating fluids. An object of this invention is to provide an arrangement of a bundle of fiat tubes for high pressure in such a manner that both alternatives will be possible.

One embodiment of the invention will now be described with reference to the accompanying drawing in which:

FIG. 1 illustrates a section of a bundle of tubes according to the invention viewed from the lateral edges of the tubes;

FIG. 2 illustrates the bundle of tubes of FIG. 1 in cross-section along the line IIII of FIG. 1;

FIG. 3 illustrates a modification of part of FIG. 2 and FIG. 4 shows on a smaller scale a section of a length of a tube of the bundle according to FIGS. 1 and 2 as viewed from one side wall of the tube.

All figures are diagrammatic and exclusively serve as examples without restricting the invention. Identical parts of the several figures are indicated by the same reference characters.

In FIGS. 1 and 2 the tubes comprise side walls 2 and 3 which are interconnected exclusively along their lateral edges by means of edge sections 2a, 2b and 3a, 3b, bent towards one another, said sections being welded together by means of an edge weld 4 while leaving the cross-sectional areas of the tubes entirely unobstructed by bridging elements. The tubes are arranged in side-by-side relation with interspaces 5 open along the lateral edges. The tubes are elongated as best shown in FIG. 4 and are in known manner arranged within a casing (not shown in the drawing) within which one heat exchanging fluid is conducted externally of the tubes in the space therebetween whereas the other heat exchanging fluid is conducted through the tubes at a pressure which may be considerably higher or lower than the pressure within the interspaces. The tendency of the side walls to bulge towards or from one another will be prevented by means of the spigot-shaped spacing elements 6 which in known manner are distributed between and (FIG. 2) welded to both sidewalls by means of electric resistance welds 7. FIG. 3 illustrates a likewise known modification of this arrangement in which the spacing elements comprise boss-like bulges 6a in the walls proper said bosses being interwelded by means of one single resistance weld 7. According to the same principle also one plane wall and one embossed wall may be interjoined. The spigots as well as the bosses may also have another cross-section shape than the circular one, such as a square shape.

Thus, the dilference between this supporting or bracing system and the known ones is that the spacing elements have been moved from the interior of the tubes to the external spaces between the tubes in which they do not form any essential obstructions to mechanical cleaning as illustrated in FIG. 4 in which the arrows indicate different directions in which a cleaning tool may be inserted into said interspaces from one side or from both sides thereof so that it will reach all parts of the walls around the spacing elements. It will be understood that if instead these spacing elements were arranged within the tube which only may be cleaned in its longitudinal direction all sections which in this direction are shadowed by the spacing elements would be practically non-accessible for such a cleaning.

The combination of the side walls exclusively welded together to tubes along the lateral edges, and the aforesaid location of the spacing elements is also very favourable for a simple and non-expensive manufacture of bundles of tubes comprising flat tubes and braced walls. Thus, a bundle according to FIGS. 1 and 2 may be formed in the following manner: Plane metal sheets adapted to form the side walls are bent at the edges and kept together pairwise in side-by-side relation at a distance corresponding to the interspace between the tubes, with the bent edges being directed away from one another. Spacing elements 6 are inserted from the side into the interspace between the plates in rows across this interspace and welds 7 are provided at the same time-between pressure electrodes embracing the plates and the interposed spacing elements. Subsequently, the pairs of plates welded together are welded by means of welds 4 so that the tubes will be formed therebetween. A tube with internally welded spacing elements may be made in a similar manner only if (in a considerably more difiicult manner) the side walls are bent subsequently to welding together the combined pairs of plates since otherwise the bent edges would prevent the spacing elements from being inserted. It is true that the arrangement of the spacing elements according to FIG. 3 eliminates this insertion step which in itself results in a simplification-which however is to be weighed against the need in this case to utilize a pressing method which is considerably more expensive than the edge bending process alone.

On the basis of the illustrated and described example anyone skilled in the art may suggest further modifications within the frame of the invention, for example sealing the tubes along the lateral edges of the side walls by other known methods, for example by folding merely one edge of the wall towards the other edge thereof or by means of ribs provided between the non-folded edges of the walls.

What I claim is:

1. In heat exchangers for heat exchange between contaminating media at high pressures of the type having a bundle of elongated flat heat transfer tubes in side by side spaced relation with interspaces therebetween for passing one heat exhanging medium inside the tubes and another heat exchanging medium in the interspaces between the tubes, a plurality of identical elongated shallow gutter elements of substantially U-shaped cross section, each shallow gutter element having a substantially flat elongated bottom between side walls extending longitudinally along said bottom, the gutter elements being arranged pairwise in registering bottom to bottom relation with an interspace between opposed bottoms, the bottoms being interconnected by spacer elements distributed in and bridging the interspaces and welded to the bottoms at all places where they abut against the bottom to form a plurality of twin gutter elements, said spacer elements having little extension in all directions parallel with the bottoms, the side walls of each shallow gutter element extending away from the interspace between the spaced bottoms of the twin gutter elements, said twingutter elements lying in such side by side relation that juxtaposed shallow gutter elements of aligned twin gutter elements have their side walls abutting throughout their length, the abutting side walls being welded together to define a plurality of elongated flat tubes of unobstructed substantially rectangular cross section, whereby the interspace between the opposed bottoms of the shallow gutter elements constitutes an interspace between adjacent tubes.

References Cited UNITED STATES PATENTS 869,822 10/1907 Wright "-152 1,215,793 2/1917 Gabrielson 165-152 FOREIGN PATENTS 107,652 7/1917 Great Britain.

FRED C. MATTERN, JR., Primary Examiner M. ANTONAKAS, Assistant Examiner US. Cl. X.R. 165170 

